In recent years, driving support display apparatuses that display a bird's-eye-view image giving a downward view of the area around a vehicle from a virtual viewpoint above the vehicle on a monitor have become increasingly popular. Many driving support display apparatuses generate a bird's-eye-view image using a plurality of cameras in order to cover a wide monitoring range.
FIG. 1 is a drawing showing a camera arrangement in a driving support display apparatus and a bird's-eye-view image obtained from images captured by the cameras.
As shown in FIG. 1, first through fourth cameras 11 through 14 are installed on vehicle 1. First through fourth cameras 11 through 14 image the road surface ahead of, behind, to the left of, and to the right of, vehicle 1, in diagonally downward directions. From captured images of first through fourth cameras 11 through 14, first through fourth camera bird's-eye-view images a through d approximating an image when looking down from a virtual viewpoint above the vehicle can be obtained.
It is desirable for a displayed bird's-eye-view image to be an image that is continuous over as wide a range as possible. Thus, provision is made for one bird's-eye-view image to be combined from captured images of a plurality of cameras. Below, a bird's-eye-view combined from captured images of a plurality of cameras is referred to as a “combined bird's-eye-view image.”
Here, an area that can be imaged by two neighboring cameras is referred to as overlap area 15. The position of an image of a pattern without height on the road surface such as a road marking or tree shadow in overlap area 15 coincides in overlap area 15 for second camera 12 and third camera 13. However, the position of an obstacle located in an overlap area differs for respective second camera 12 and third camera 13 bird's-eye-view images due to the fact that the obstacle has height.
This point will be explained using FIG. 2. FIG. 2 is a drawing explaining the fact that an obstacle disappears at a boundary line. This is because projection direction 18 of an obstacle when viewed from second camera 12 is different from projection direction 19 of the obstacle when viewed from third camera 13.
Thus, the direction of foreshortening (projection direction) of an obstacle in overlap area 15 differs for each bird's-eye-view image of each camera. When a camera image is delimited by a boundary line as in FIG. 2 in overlap area 15, bird's-eye-view image area b generates a bird's-eye-view image using a second camera 12 image. Similarly, bird's-eye-view image area c generates a bird's-eye-view image using a third camera 13 image. Consequently, obstacle 16 present in the vicinity of a boundary line is not displayed in either a second camera 12 bird's-eye-view image or a third camera 13 bird's-eye-view image.
There is consequently a problem in that, when a boundary and an obstacle overlap, the obstacle disappears, and the obstacle is not visible to a user.
An apparatus disclosed in Patent Literature 1, for example, is known as a driving support display apparatus that solves this problem. FIG. 3 is a drawing for explaining Patent Literature 1. In Patent Literature 1, when display of obstacle 16 overlaps boundary 17 of composite images as in FIG. 3 (a), the boundary is changed so that the display of obstacle 16 does not overlap boundary 17 and an image with boundary 18 is displayed as in FIG. 3 (b).